Conventionally, since nylon balloons and inflatable toys of polyethylene or the like can not be subjected to a high frequency working, these materials have been made such that a heating plate with an overall shape is prepared by a copper or aluminum plate, and pressed onto laminated plastic sheets by means of a press mechanism, while always heating the plate, to fuse bond the laminated plastic sheets, and the fuse bonded plastic sheets are cut, except for thin sheets, by a separately prepared cutter with the overall shape.
However, a material for the inflatable toy of polyethylene or the like is very thin, such as 0.1 to 0.3 mm, if two sheets are laminated. Moreover, if an edge of the cutter is not equally applied to the sheets, inferior portions are formed. Therefore, a mold has been prepared by casting a material which is hardly distorted by heat, scraping and grinding. Especially, in the balloons made of aluminum vapour deposition nylon or the like, the sheet has a very thin thickness, such as one half of that of an ordinary sheet, and requires a high fuse bonding temperature, so that the press mechanism as well as the mold is required to be precise, and the cutter is also very expensive.
Also, as a simple method, the inflatable toys of polyethylene or the like have been prepared by a ball sealing method, wherein fuse bonding and fuse cutting are carried out by using a heater prepared by cutting a nichrome plate along an object configuration in a belt shape with a narrow width, and welding and fixing a thin nichrome wire on the nichrome plate.
However, in the ball sealing method, the nichrome belt has to be formed by cutting along the object configuration from the large plate with the same width from the beginning to the end, so that it is difficult to form. Moreover, since the wire material and the belt material are not always the same quality, these materials move due to expansion discrepancies, resulting in a short life of a product. Further, since the aluminum vapour deposition nylon or the like can not be fuse-cut by this method, this method is not suitable for manufacturing the balloons.
As a further simple method, it has been widely practiced that a plastic sheet is fuse-cut by a straight thin nichrome wire, but since the fuse cut portion can not be strongly fuse-bonded, this method can not be used for fuse-bonding.
Further, for nylon balloons and inflatable polyethylene toys, it is impossible that projections, such as hands and legs, are added to a body by a post-working as for a vinyl working. Therefore, a plastic sheet gusset folded in a W-shape is prepared, a separating agent is applied to the inside of the W-shaped gusset, and the plastic sheet is pressed by a heat mold from the outside thereof to make a nylon balloon and a polyethylene toy. However, in this method, since the body is made of two sheets and the projections are made of four sheets, resulting in different thicknesses, a boundary line between the body and the projections is sealed weakly, and the control of the working temperature of the mold is difficult. Especially, when a temperature is raised such that the four sheets of nylon balloon can be fuse-cut, the nylon material at the sealing boundary line which is once fused and solidified again is liable to break, and therefore products can not be made by this method.